1. Field of the Invention
The present invention relates to soldered articles, and more particularly, the invention relates to a soldered article including a component having a Cu conductor joined with a solder.
2. Description of the Related Art
Solders have been widely used as jointing materials for achieving electrical and mechanical connections in electronic equipment and electronic components.
On the other hand, as a material for constituting electrodes in electronic equipment and electronic components, Cu has been widely used in view of its corrosion resistance, costs, etc.
Soldered articles in which the electrodes composed of Cu are joined to objects (for example, lands on mounting substrates) have been widely used for various applications.
Although solders having Sn and Pb as major constituents have generally been used, in consideration of environmental protection, solders having Sn as a major constituent, and excluding hazardous Pb, (hereinafter referred to as "lead-free solders") have come into use.
However, in a soldered article in which electrodes composed of Cu are joined to a mount object using a lead-free solder having Sn as a major constituent, leaching easily occurs at the electrical junction during soldering.
In comparison with the case when conventional Sn--Pb based solders are used, lead-free solders having Sn as a major constituent are inferior in solderability and joining strength at soldered sections, and are less reliable.
In order to overcome the problems described above, Sn--Cu--Bi-based solders containing Ag have been disclosed (for example, Japanese Unexamined Patent Publication Nos. 2-70033, 5-228685, and 8-132277). However, the solders in the above patent publications contain Ag, resulting in an increased cost.